The Philadelphia Daily News reports the pair of peregrine falcons that are nesting there have four new baby falcons. Arthur McMorris, the peregrine falcon coordinator for the Pennsylvania Game Commission, says the baby birds are about 30 days old.

The adult falcon pair began nesting in a man-made nesting box on City Hall's tower in 2009, after it had sat empty for nine years. They moved out in 2010, but returned in 2011.

McMorris says peregrine falcons have been taken off the federal list of endangered species, but remain endangered in Pennsylvania. The pair of adult birds in the City Hall tower is one of just 33 pairs known in the state.

The pair has been aggressive towards anyone who has tried to sneak a peak in the nest -- something that McMorris says is good.